feat(.devcontainer): basic codespaces config (#48484)

Co-authored-by: Mrugesh Mohapatra <1884376+raisedadead@users.noreply.github.com>

.devcontainer/docs/devcontainer.json

@@ -0,0 +1,24 @@
+{
+  "context": "../..",
+  "customizations": {
+    "codespaces": {
+      "openFiles": ["docs/how-to-work-on-the-docs-theme.md"]
+    },
+    "vscode": {
+      "extensions": [
+        "dbaeumer.vscode-eslint",
+        "esbenp.prettier-vscode",
+        "freeCodeCamp.freecodecamp-dark-vscode-theme"
+      ]
+    }
+  },
+  "dockerFile": "Dockerfile",
+  "forwardPorts": [3400],
+  "portsAttributes": {
+    "3400": {
+      "label": "Docs",
+      "onAutoForward": "openPreview"
+    }
+  },
+  "postAttachCommand": "npm run docs:serve"
+}